It was only about that fast on the nForce2, back in the 90's, because it was connected to a CPU that was only made for single-channel DDR RAM with the original AMD Athlon.

Nowadays, with CPU's made and intended to run with such an amount of bandwidth, the gains are more significant. I certainly would not even dream of trying to run a Skylake on single-channel mode. If you have to do that, it's more likely a defective motherboard or CPU.

The X99-based i7's practically could even go quad-channel, with most motherboards for that style of chip having eight RAM slots.